Surface Roughness of CoCr and ZrO₂ Femoral Heads with Metal Transfer: A Retrieval and Wear Simulator Study

Abstract

Metal transfer to femoral heads may result from impingement against the metallic acetabular shell following subluxation/dislocation, or when metallic debris enters the articulation zone. Such transfers roughen the head surface, increasing polyethylene wear in total hip replacements. Presently, we examined the surface roughness of retrieved femoral heads with metallic transfer. Profilometry revealed roughness averages in regions of metal transfer averaging 0.380 μm for CoCr and 0.294 μm for ZrO2 which were one order of magnitude higher than those from non-implanted controls. Scanning electron microscopy (SEM) revealed adherent transfers on these retrievals, with titanium presence confirmed by electron dispersive spectroscopy. Due to the concern for increased wear, metal transfer was induced on non-implanted heads, which were then articulated against flat polyethylene discs in multidirectional sliding wear tests. Increased polyethylene wear was associated with these specimens as compared to unaltered controls. SEM imaging provided visual evidence that the transfers remained adherent following the wear tests. Pre- and post-test roughness averages exceeded 1 μm for both the CoCr and ZrO2 heads. Overall, these results suggest that metal transfer increases the surface roughness of CoCr and ZrO2 femoral heads and that the transfers may remain adherent following articulation against polyethylene, leading to increased polyethylene wear.

Chromium nitride coating for large diameter metal-on-polyethylene hip bearings under extreme adverse hip simulator conditions

“…These roughness values were similar to retrieved bearings [31,32,36,37]. The wear rate and cobalt release during this phase of testing was not interpreted as clinically relevant due to the abrasives used.…”

Structure and composition of silicon nitride and silicon carbon nitride coatings for joint replacements

“…Low Ra and rms values of coatings deposited on Si are promising for joint bearing applications [32,[43][44][45]. However, when deposited on CoCr substrates, which are rougher than Si-wafers, the surface roughness of the coating will also increase.…”

Wear Performance of Sequentially Cross-Linked Polyethylene Inserts against Ion-Treated CoCr, TiNbN-Coated CoCr and Al2O3 Ceramic Femoral Heads for Total Hip Replacement

“…Femoral heads made of a cobalt-chromium (CoCr) alloy are commonly used in total hip arthroplasty, owing to their beneficial combination of mechanical strength and ductility. In contrast, their clinical success is limited by the loss of their smooth surface over time, resulting in a greater counterface roughness and accelerated polyethylene wear [9][10][11]. Popular alternatives to CoCr alloys are oxide ceramics, which are classified to be the reference in the field of hard-on-soft bearings.…”